Conventionally, caps are applied automatically to respective containers by machine units equipped generally with a plurality of capping assemblies, set in motion by a carousel or similar supporting structure in such a way as to revolve around a vertical axis of rotation.
In addition, each assembly is generally rotatable about a respective axis parallel to the vertical axis of the carousel, and capable also of axial motion on the carousel in such a way as to move toward or away from a corresponding container moving as one with the carousel.
Each capping assembly is equipped normally with a respective gripping apparatus, typically a conventional gripper or a similar device, by which a screw cap can be taken up, held and twisted onto the threaded neck of a respective container when a moving part of the capping assembly is set in rotation.
In general, an apparatus of the type in question presents two or more arms, each hinged to a bottom end of the relative capping assembly in such a way that a pivoting movement on the hinge pin will cause a gripping end of the arm to move in and toward or out and away from the rotational axis of the assembly. It will be clear that the inward or outward movement of each arm occurs simultaneously with the inward or outward movement of the other arms, in such a way as will cause the gripper to contract and tighten, or to spread open.
The free end of each arm is fitted with a rubber pad positioned to engage in direct contact with a lateral cylindrical portion of a cap about to be applied to the neck of a filled container advancing on the carousel.
The part of the rubber portion designed to engage the cap is generally of arcuate geometry, presenting a profile substantially matched to the outer lateral profile of the cap currently in use.
The rubber pad is fixed generally to an adapter that will be mounted to a relative structural member of the corresponding gripper arm by means of two or more fixing screws so that it can be removed and replaced with an adapter having a structurally different gripping pad, that is to say, of shape and/or dimensions dissimilar to the shape and/or dimensions of the gripping pad presented by the adapter removed from the arm, or alternatively, in the event of wear or damage, replaced with a new adapter presenting the same structural characteristics as the one removed.
Whilst the gripping apparatuses currently in use are able to apply caps to containers satisfactorily, the applicant finds nonetheless that they are not entirely free of drawbacks and could be improved in a number of respects, mainly with regard to the simplicity and practicality of the operation by which the adapters presenting the rubber pads are removed from and refitted to the arms of the gripper, but with regard also to the time needed to carry out the steps of removing and fitting the adapters, and the cost disadvantages connected with these same removal and refitment operations.
In particular, the operations of removing and refitting the aforementioned adapters involve unfastening or fastening two or more fixing screws for each arm of each gripper operating on the capping units currently in use. Consequently, given the appreciable number of grippers normally in operation on conventional capping units, and therefore the appreciable number of single arms carrying respective adapters, these removal and refitment procedures tend to be significantly long and somewhat impractical. In effect, such procedures necessarily involve loosening or tightening all of the fixing screws present on the arms of each apparatus, one by one. The operations in question represent an even greater burden when there is a change of production size involved, in other words, a changeover requiring the replacement of all the adapters in use on the grippers of a given capping unit with others presenting rubber pads of different size and shape, suitable for handling caps that are structurally dissimilar to those utilized in production previously. In this instance, a size changeover requires twice the time needed for a straight replacement, since the procedure involves undoing all the fixing screws to effect the complete removal of all the existing adapters, then positioning all of the adapters for the new size or style of cap and retightening all the fixing screws needed to clamp the repositioned adapters.
The same problem arises when, as a result of the rubber pads becoming worn and degraded, the adapters installed originally with the gripper arms need to be renewed completely by fitting replacement adapters with fresh rubber pads.
Moreover, given the complexity of the prior art capping units in question, the operating space needed to effect the removal and/or refitment of the adapters is somewhat limited, with the result that the tasks of loosening and/or tightening clamp screws employing conventional instruments, equipment and/or tools such as keys, screwdrivers and the like, tend to be obstructed and consequently prolonged.
Finally, it will be appreciated that these tasks can be carried out on capping units only when not in operation. Indeed in practice, the capping units are shut down by suspending the entire packaging process temporarily. Self-evidently, every time the adapters of the gripping apparatus need to be replaced or renewed, the operation impacts significantly on the cost of capping the containers, as a proportion of overall production costs.
To overcome the drawbacks associated with the removal and/or refitment of these gripper adapters, it is the common practice to procure a broad selection of capping assemblies equipped with components configured for caps of different sizes and styles, so that when the need arises to effect a size changeover or to renew worn parts, this can be achieved more simply by replacing the entire gripping assembly rather than the single adapters. With this strategy, the operation of the capping units can be restored more quickly when interrupted momentarily, and the adapters of any assemblies removed from the line can be replaced as required, and at leisure. However, the expedient of preparing numerous sets of gripper assemblies each dedicated to a particular cap size, simply in order to minimize down time during the production cycle, is economically expensive and has little advantage.